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From: Frank Reed (no email)
Date: Sat Mar 04 2006 - 00:19:49 EST
I wrote in my original post in this thread:
"The CWM was already 56 years old on this voyage, and whaling was a minor
business in the 1890s, so maybe it's not surprising that there's no "rocket
science" in this navigation. Nonetheless, this very simple celestial was good
enough to cross the Pacific from California to Micronesia and then on to Japan."
And in a later message I wrote:
"That's how it was done for decades on ships at sea even as late
the 1940s. With all the talk recently on Sumner's method, I think it's worth
remembering that Sumner's lines were considered a somewhat exotic technique,
one that might never be used in months at sea. Celestial lines of position
didn't catch on universally until almost a century after Sumner published.
And
why that was the case is still a fascinating question... "
George H, you replied:
"To me, that's one of those sweeping statements, that cries out for a bit of
backup evidence. There is much evidence to the contrary."
I would love to see some!
Evidence in this business can be a tricky thing. For example, if you open a
copy of Bowditch from about 1850 to 1880, you might think that "lunars" were
an important thing, since many pages are devoted to them, while in reality,
they seem to have gone nearly extinct by about 1855. Meanwhile, if you open a
Bowditch from the same period and look for Sumner's method, you'll find only a
half-page treatment. It would be equally unwise to treat this as evidence
regarding Sumner's method. Of course, given the popularity of Bowditch's
Navigator, it surely didn't help. I'm not saying that you can never use the
navigation textbooks as evidence of actual practice, but that evidence has to be
interpreted carefully.
Logbooks, navigational notebooks, oral histories (for the later period),
those are the sorts of things that we can rely on as evidence of navigational
practice.
And you also wrote:
"In his "Wrinkles in practical navigation" (1881), Lecky, a practical
navigator if ever there was one, and no academic, states that his chapters XI, on
Sumner Lines, and XII, on Double Altitudes, are the most important in the
book."
Yes, and at this date, forty years after Sumner's publication, Lecky still
has to explain this AFTER detailing longitude by time sights. He's "selling"
Sumner's approach as if it is something unusual. And why is he doing this?
Because, as he puts it, this will help the navigator to "understand the
principle of the problem". He further notes that "it is not always convenient to draw
Sumner lines on a chart" [imho, this is a BIG factor] and suggests that one
should work the problem by calculation rather than plotting. This calculation
is, as Lecky puts it, "a formidable affair, and the rules at the finish are
so complicated as to scare most ordinary seafaring men."
George, you added:
"He tells us that within a year of Sumner's publication, an order was given
to supply a copy to every ship in the US Navy!"
That's actually a quotation from the preface of one edition of Sumner's
booklet (it was from a letter written by the famous M.F. Maury). What does it
tell us? Well, it tells us that Maury ordered, or promised to order, a lot of
books! It also tells us that Sumner's conception of navigation received wide
"critical acclaim" from experts (and it certainly did). It tells us little
about actual practice at sea.
And you concluded:
"So I wonder whether that statement is based on a biased sample of
navigationally backward or ultra-conservative mariners; such as, perhaps, American
whaling vessels. "
Certainly the SPECIFIC case the Charles W. Morgan in 1896-97 should be
interpreted with that in mind. That's what I said in my original post on the topic
(!). There were definitely navigators who used Sumner lines in the late 19th
century, but they seem to have been rather exceptional. And there were still
thousands of navigators even in the 1930s doing nothing but Noon Sun and
morning/afternoon time sights of the Sun even forty years after that voyage.
I have not examined even a small fraction of the logbooks in the vast
collection at Mystic Seaport, but so far I have not found a single example of
Sumner lines, Sumner line calculations, or even references to the technique in the
19th century, outside of navigation textbooks. Don Treworgy encountered ONE
reference to a Sumner line in a logbook from the 1880s in the collection. The
navigator in question, Charles H. Townshend, was famously experimental. For
example, he shot Jupiter in daylight as a challenge. He mentions, just once,
that he "tried Sumner's method. Seems to work." (or words close to that).
I'll mention here one specific problem with Sumner's method. He explicitly
refers to Mercator's projection. This is un-necessary. If he had simply
described a method for plotting on a plain sheet of paper, the method might have
been seen as much more practical by navigators. In fact, for what it's worth,
in the 1903 revision of Bowditch a rather long explanation was inserted on
this very point.
The transition to celestial lines of position as the unversal standard for
celestial navigation was very slow, and the reasons are not entirely trivial.
To avoid potential mis-reading, I am not suggesting that Sumner lines were
never used. I still like my earlier phrasing: Sumner's method was considered a
"somewhat exotic technique".
-FER
42.0N 87.7W, or 41.4N 72.1W.
www.HistoricalAtlas.com/lunars
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